Cashew Nut Shell Liquid (CNSL) extracted from cashew nut shell, is a dark viscous oil which contains Anacardic acid (80.9%) and Cardol (10-15%) along with some other minor material components has found numerous applications in Paints and Enamels, Electrical Insulation Vanish, Polymer, Lamination, Rubber Products/Brake Linings, Adhesive and Pesticides. Even the tree exudes a gum that can be used in varnishes or in place of gum Arabic.

India, Vietnam and Indonesia are the major cashew producing countries followed by Philippines, Malaysia, Thailand and Sri-Lanka. India being the largest producer of raw cashew nut in the world has more than 45 cashew cultivars, 1.01 million hectares under cultivation and 0.75 million tons product. African countries producing cashew are Côte d’Ivoire, Nigeria, Tanzania, Mozambique, Kenya, Benin, Guinea-Bissau, Mozambique, Ghana, Senegal and Madagascar while Latin American countries producing cashew consist of Brazil, Columbia, Costa Rica, Honduras and Salvador.

Recent technological interventions have radically changed the cashew sector. Vietnam is the world leader in cashew nut processing with fully automatic cashew processing units being successfully operated while India is the second world leader in cashew nut processing with semi-automatic units being successfully operated. As revealed by Cashew Info, 2017, in the international market, RCN is sold for about $4.7 per Pound (0.45kg).

Steps Involved in Raw Cashew Nut Processing

1. Drying of RCN: Freshly harvested RCN are dried by spreading it on the drying yard under the sun for the period of 1-3 days depending on the moisture content. The nut making ratting sound is the symbol that the raw nuts have been dried properly. However, it is necessary to monitor the drying process as over drying of RCN may cause scorched kernel which may lead to higher breakage during shelling. On the other hand, improper drying of RCN may again cause lower yield of wholes and de-colouring of kernel.

2. Preparation/Construction of Drying Yard – In general, for drying 100 bags (8000kg) of RCN around 700 sq. feet of drying yard area is required. The size may differ from processor to processors depending on the total area they possess within their processing premise. The drying yard should be constructed with 1.5-2 inch (4 – 5 cm) thick cement concrete floor over flat solid brick or bolder stones.

3. Drying Process – Once RCN is received at the drying premises, the processors should check the moisture level by using moisture meter or some traditional method like poking pointed pin or nails and based on which days of drying is decided. Processors will avoid buying the RCN having more than 17-18% moisture as it may be immature. The RCN is spread on the drying yard throughout the day and kept in covered place during the night. Once the RCN is dried, it is calibrated, bagged, weighted and tagged with details before sending it to warehouse. In general, during the warehousing or storage, the RCN will be carrying 6-9% moisture level.

4. Calibration Process – It is also called size grading and pre-cleaning of the nuts. At this stage, the dried RCN is separated as per the nut size as well as impurities like dust, plant stalks, mud/stones etc. are removed. This practice is newly adopted by the processors as it is not only very useful in efficient utilization of shelling machine but enhancing the manual cutting/shelling rate also. In this process a calibrator/grader machine is used, the machine will have cylinder shaped sieves having whole of various dimensions/size and RCN passed through different wholes will be segregated and collected separately. The size of the whole varies from 17-18 mm to 23-24 mm which may yield 3-5 grades of RCN. However, as per the requirement of the customer the number of grades can vary. In general, the processors would grade the RCN mainly into the three sizes, i.e. small, medium and big.

5. Equipment/machines Used – Calibrator/grader machine of various capacities and sizes are available in the market. The capacity ranges from 1000 kg/hr to 2000 kg/hr and dimensions from 5 feet (length) to 20 feet based to the number of grades sorted by the machine. Some large machines would have attached elevator for feeding and screw conveyor for separating the nuts. A simple grader machine with manual feeding options of 1000 kg/hr capacity would require 1 HP (horse power) motor and based on the additional attachments, it may increase up to 4-5 HP. Selecting the capacity of machine is irrespective of plant capacity as the raw nut is stored after calibrating, in general the size or capacity of this equipment is 3-5 times higher of the processing capacity.

6. Storage/warehousing – Dried, cleaned, calibrated, bagged and tagged/marked RCN is stored in warehouses for export or future use. Jute bags are used for bagging RCN and 80kg is the standard quantity stuffed in a bag. Based on the origin, grade, purchase date etc; different lots are created, bagged and stacked accordingly. Warehousing is an important activity not only from the safe storage point of view but also from the traceability of the nuts point of view.

7. Construction of Warehouses – A lot of guidelines are available on the civil construction of the warehouse. Processors will follow the guideline as per their convenience. In general, the floor of the ware house should be 1.2-1.5 meter above the ground level, flooring should be done using solid bricks and cement plaster above, structure height of 4.6m from plinth level of the building and single span of tubular truss with colour-coated dyna sheet roofing.

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